VMS EXCHANGE format for VAX console media

[Johnny Billquist]

On 2015-06-06 01:57, Mark J. Blair wrote:
> I have a copy of an 11/730 console tape which I have been told is in EXCHANGE format as created by the CONSCOPY utility. Can any of the VMS experts here help this VMS noob learn how to translate that into a raw block-level image of the corresponding TU58 tape, which I might be able to use with a TU58 emulator?
>
> I see that the EXCHANGE image is 512 bytes longer than a full TU58 tape. Could it be as simple as chopping off the first or last 512 bytes? I'm not quite at the point yet where I know what a console tape ought to look like in a hex editor, so I can't clearly see whether that might work yet.
>
> I'm presently starting to work on getting some version of VMS running on an emulated 11/780 under simh. So with any luck, I may have a functioning VMS environment before too long, even though I haven't managed to boot up my real 11/730 yet. My end goal is to use that console tape image with some TU58 emulator to boot up my real VAX. I have some original console tapes for it, but they no longer seem to be readable. I did get my machine to examine one of them quite a bit before deciding it wasn't suitable, so maybe there is still some recoverable data on those tapes... but none of them seem to be sufficiently error-free to boot my machine.
>
> I'm presently working on booting it from a downloaded console tape image, but getting tu58em and my 11/730 to like each other is still an ongoing project. Once I get there, I think that this EXCHANGE format image that I have is the same console tape version as my unreadable real tapes, and newer than the other downloaded image that I'm presently trying to use, so it would be nice to be able to get it into a format that I can use directly.
>
> Thanks in advance for any clues!

Unless I'm really confused, "EXCHANGE" is not a format. EXCHANGE is a 
program under VMS to read/write RT-11 format file systems, which is what 
you usually had on the FE media.

However, if you actually have EXCHANGE create an image copy of a 
tape/disk, and it actually is 512 bytes larger than the device, then I 
guess EXCHANGE have some sort of image dump format with some extra block 
with some meta-data.

See if you can spot the RT-11 file system in there.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
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